Polyangiitis overlap syndrome with eosinophilia associated with an elevated serum level of major basic protein

Polyangiitis overlap syndrome is a new disease entity and the reported cases in the literature are still limited. We describe a female patient presenting with finger ulcers, skin eruptions, pleural effusion, interstitial pneumonia and eosinophilia. Skin biopsy showed systemic small-sized angiitis and thrombosis. She was diagnosed as having polyangiitis overlap syndrome and was successfully then treated with corticosteroid. It is also of interest that the disease activity was correlated with the number of eosinophils in peripheral blood. The measurement of the serum level of major basic protein released from eosinophils functioning as a coagulant indicated the possible association of eosinophilia with thrombosis and polyangiitis.